Ultra high frequency impedance adjustment means

ABSTRACT

An improved cavity type ultra high frequency impedance matching means in which tuning is accomplished by providing the inner and outer conductors of a feed line having a relatively small diameter as compared to an associated tuning cavity means and in which the shorting disc comprises radially moveable, spring biased wedge means for releasably locking the shorting disc in desired adjusted position and release operating means connected to release the wedged portions of the disc and sliding the disc to a new adjusted position for impedance adjustment.

United States Patent Phillips [451 Sept. 9, 1975 [54] ULTRA HIGHFREQUENCY IMPEDANCE 2,796,587 6/1957 Phillips 333/33 ADJUSTMENT MEANS2,901,712 8/1959 Hogg 333/33 [75] Inventor: Edwin N. Phillips, WinterPark, Fla.

[73] Assignee: The United States of America as represented by theSecretary of the Navy, Washington, DC. 22 Filed: July 10, 1974 [2]]App]. No: 487,115

[52] US. Cl 333/33; 333/97 R; 331/96; 330/31; 330/56 [51] Int. Cl.*....HOIP 5/00; HOlP 1/28; HO3H 7/38 [58] Field of Search 330/56, 31;315/3953; 333/33, 97 R; 331/96, 101, 103

[56] References Cited UNITED STATES PATENTS 2,203,806 6/1940 Wolf 333/97R 2,763,842 9/1956 Olive 333/33 A /0 Z V CONTROL GRID :3 z x 2 0 CA114005 2 /7 N 30 I5 SHORT CAVI TY CIRCUITED J T 26 MAIN SHOR TING PISTON FEED Primary ExaminerPaul L. Gensler Attorney, Agent, orFirm-Richard S. Sciascia; John W. Pease ABSTRACT 6 Claims, 11 DrawingFigures OUTER CONDUCTOR 62 CAPT/VA TED TENS/0N SPRING SPLIT ANNULUSACTUATOR BASE l2 CONTROL DISCS PATENTED SEP 9 I975 SHEET 1 BF 4 kmQImPATENTEDSEP 191s snwau g OUTER CONDUCTOR INNER CONDUCTOR OUTER C'ONDUCTOR ANNULAR 64 SHOE SLIDING WEDGE SLIDING WEDGE PISTON CAPT/VA TEDTENS/0N SPRING SPLIT ANNULUS b ACTUATOR RODS ACTUATOR BASE I2 CONTROLDISCS FIG.2'A-

- SLIDING WEDGE CASCADE UPPER SLIDING WEDGE 78 COMPRESSION SPRING 72 LyLOWER SLIDING WEDGE FIG. 3

J z ACTUATOR RODS OUTSIDE BASE- IZ CONTROL DISKS FINGER STRIP TOP 8BOTTOM I SLIDING- WEDGE A SSEMBL Y WITH FINGERED- BARREL COMPRESSIONSPRING LOWER SLIDE WEDGE FIG. 4

UPPER 62 WEDGE 60 TRAIN l I 96 I I SLIDING- WEDGE-CASCADE I ALONG OUTERCONDUCTOR I I02 X- INNER ANNULAR b D SHOE LOWER WEDGE TRAIN W FIG. 5

PATENTED 1 75 suwuuig 62 OUTER CONDUCTOR INNER CONDUC TOR E Ma TD SM awU56 U83 004 MP6 CP- p m RMB wmw SUD R IE N W E R Mi h PE 6 INNER OUTERUPPER WEDGE RACE 6 m m A F m D E w w M V! R R W T E E R S W W E R R V DuE D D m M A 0 0 W M w M 0 3 RE M M a 6 T L M N6 Y Y L 0W AP T T Y L 5 5T ,A J I S 1 w f 6 W STYL/ZED PLA TE ULTRA HIGH FREQUENCY IMPEDANCEADJUSTMENT MEANS BACKGROUND OF THE INVENTION The invention relates tothe field of coupling networks and in particular to those having longline elements where a function of adjustable match or mismatch isrequired.

In impedance matching means wherein a slidable disc member is employedfor the purpose of adjusting impedance match such units have been foundunsatisfactory in application to a small bore cable employing wire orfilamentary type inner conductors. It has been found impossible toconstruct a shorting disc which can be made adjustable and which willprovide reliable results in maintaining satisfactory electrical contact.With other than wire (or filamentary type) inner conductors, a varietyof contacting means are known to have been successfully employed andhave included finger strips having a plurality of fingers to abut thecylinder wall from a short-circuiting disc edge; coil springs which arepreformed and then cocked in an annular slot to give a multiplicity ofcontacting points; and similar devices. However, none of these can beapplied successfully to the wire-like small diameter of the innerconductor of an air-cored coaxial line of small diameter.

SUMMARY OF THE INVENTION To provide for the deficiencies noted above thesubject invention provides an improved cavity type ultra high frequencyimpedance adjustment means in which the short-circuiting piston is inthe form of an arrangement of a chuck having a plurality of wedges whosegripping surfaces can be engaged normally under spring pressure butwhich can be released from outside the structure so that movement of thecomposite piston along the line axis can be effected with the fingersretracted. Operating means connected to act upon the spring means torelease the wedge bias on the disc elements are provided so that thedisc can be moved to a new position for impedance matching adjustment.

DESCRIPTION OF THE DRAWING FIG. 1 is an elevational view of an inputcircuit of a UHF (ultra high frequency) amplifier used as an impedancematching device applied to a vacuum tube amplifier and incorporating ashorting disc incorporating the invention;

FIGS. 1A, 1B and 1C are a schematic electrical diagram and Smith ChartMaps used to explain the matching function of the apparatus of FIG. 1;

FIG. 1D shows in schematic a modification of the apparatus of FIG. 1 toutilize a transistor instead of a tube for amplification;

FIGS. 2 through 6 are cross sectional views of several preferredembodiments of the disc and actuator portions of the impedanceadjustment means of FIG. 1;

FIG. 2A is a plan view of the segmented disc arrangement of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the field of oscillators andamplifiers used at very high frequencies (in particular the region lyingroughly between 100 and 1000 megacycles per second), the housing of theactive part of the system is commonly called a cavity. Such structuresare actually devices for providing the appropriate impedancetransformations at the input and output ends of the assembly. The termcavity is used in this sense in the writings hereinafter.

Referring to FIG. 1, the arrangement of concentric tubes 12 and 14represent the input circuit of a UHF amplifier indicated generally at 10which has a tunable feed transmission line circuit generally indicatedat 15 and which includes an incoming section 17 and a tuning section 19.Each of the sections 17 and 19 comprise coaxial conductors having outerconductor 16 enclosing inner conductor 18. A disc shorting means 20 isprovided in section 19. The load on the impedance matching circuit,including the elements mentioned above, can be the input part of avacuum tube represented in FIG. 1 by the control grid 22 and cathode 24.The interspace between the control grid 22 and the cathode 24 presentsan impedance which requires matching to the incoming coaxialtransmission line 15. An arrow head 26 shows the direction of flow ofthe incoming incident power. While a vacuum tube input is shown in FIG.1 as the load for the impedance matching (adjusting) means including thecoaxial input line 15 and its associated adjustable shorting disc 20, itcould equally well be the input circuit of a UHF transistor typeamplifier (shown in FIG. 1D) between its base and emitter elements, andit could equally well be the input circuit of a UHF travelling wave tubeor other amplifying device (not shown).

In FIG. 1 the outer conductor 16 of the incoming section 17 of the feedtransmission line 15 is fastened to the inner wall of outer tube 14 allthe way along until the outer conductor 16 stops at its meeting with thecontrol grid 22. The inner conductor 18 of the same incoming line 15continues across the physical gap between the control grid 22 andcathode 24 and it there continues as the inner conductor (still referredto as 18) of the tuning section 19 with its outer conductor maintainingthe identification 16. The outer conductor 16 of tuning section 19 isconductively fastened to the outer wall of tube 12. Solder or othersuitable means can be used to conductively fasten the respectiveconductors l6 and tubes 12 and 14. The inner conductor 18 is stopped(electrically) by the small short circuiting disc 20, although it mayphysically continue through the center of the disc 20, as indicated, forsuch purpose as constructional anchoring.

In FIG. 1 the incoming UHF power flows into the feed T/L (feedtransmission line) 15 as indicated by the arrow 26. It is at the gap inthe outer conductors of the two small'bore coaxial line sections 17-19that interest centers. The mismatched load lies in parallel with theportion of the main cavity between the grid-cathode gap and the mainshorting piston 28 shown in the diagram. This axial length indicated bythe bracket 30 is generally shorter than a quarter wavelength so that itshows an inductive reactance, 32, (FIG. 1A) at the gap, this being inshunt with the parallel resistance 34 and capacitance 36 presented bythe tubes input circuit. This reactance is shown on the assembly diagramas X /Z 2 being the cavity surge impedance. Hence, at any one frequency,it can be represented as a coil in shunt with the mismatched load Z Allof these impedances are ultimately normalized against the surge impe'dance Z of the incoming Feed-T/L 15. Because of the gap in the outerconductor of the incoming Feed-T/L 15, the paralleled combination of thecavity reactance and the mismatched load impedance is in series with theincoming Feed-T/L through the small-bore coaxial cable section 19 whichextends down along the inner conductor 12 outer wall, this being calleda shortcircuited T/L. Only when the combined currents from the cavityreactor and the mismatched load flow down the inner surface of this linesection 19 outer conductor 16, across the small short-circuiting disc20, and up this lines inner conductor 18, can they then flow out throughthe inner conductor 18 of the Feed-T/L 15, section 17, and complete thecircuit. Hence, the input reactance of this captive small-boreshort-circuited T/ L section 19 must be in series with the paralleledload and reactor; accordingly, it is shown as a series coil 38 at thehead end of the circuit (see FIG. 1A). When, as is usual, thisshort-circuited T/L section 19 is less than a quarter wavelength inaxial length, it can be represented as an inductor at its input port.The normalization to the 2., base through the separate multipliers isshown on the schematic FIG. 1A.

The impedance range over which this ell-network will match is showndiagrammatically in FIG. 1B and 1C. The extremes are shown as limit arcsand limit points, and these form the area shown in FIG. 18. Fortunately,most UHF matching in these circumstances involves the same paralleledcombination of resistance and capacitance mentioned in the foregoing(i.e., the input impedance of a UHF tube or transistor), so that thisarrangement of inductors will match, as the Smith Chart map indicates inFIGS. 18 and 1C.

FIG. 1D is a partial redrawing of FIG. 1 showing how the invention wouldbe applied to a transistor in place of a tube amplifier. Thus, the outerconductor 16 of line section 17 is connected to the base 31 of atransistor 33 and the outer conductor 16 of line section 19 is connectedvia plate 35 to the emitter 37 of the transis tor 33. This apparatuswith the transistor 33 operates in the same manner as described for thetube amplifier arrangement of FIG. 1.

In order to carry out the adjustment of the frequency impedanceadjustment means of FIGS. 1 and 1D it is necessary that the shortingdisc 20, (also commonly referred to as a piston) be applicable foroperation between the inner and outer conductors of a wire-like aircoredcoaxial line of small diameter and that it be man ufacturable,externally adjustable, and reliable in contact with both the inner andouter conductors.

In accordance with a further aspect of the invention the shortcircuiting piston is that of a chuck whose grasping surfaces can beengaged normally under spring pressure but which can be released fromoutside the structure so that movement of the composite shorting pistonalong the line axis can be effected with the fingers retracted. Severalpreferred embodiments of the short circuiting piston and operating meansare shown in FIGS. 2 through 6.

In one embodiment, as shown in FIG. 2, a spring biased wedge meanas isprovided which comprises an annulus, generally indicted at 40, split toform inclined adjacent surfaces 42, 44 and segmented to formcombinations of inner annulus wedge segments 46 and outer annulus wedgesegments 48. Each pair of associated inner and outer wedges 46, 48 arereacessed as at 50, 52 to receive a captive tension spring 54. Extendingthrough each spring coil and extending to the dead outside space of thecavity are provided actuator rods 56 which connect to outside base platecontrol discs 58.

FIG. 2A shows a plan view of the segmented discs of FIG. 2. When notcompressed for sliding the wedges, the spring 54 holds its associatedpair of inner and outer wedges securely tight and in good electricalcontact with the respective inner conductor 60 and outer conductor 62.Pushing the outside base control discs 58, 59 together urges the wedges46, 48 away from interface with the inner and outer conductors so thatthe whole assembly can be moved axially to a new adjusted location. Disc59 is connected by rod 57 to the lower wedge 48 as indicated.

In another embodiment of the spring biased wedge means, as shown in FIG.3, an annulus is segmented to form outer shoes 64 for engaging the outerconductor 62 and each shoe is recessed to form a V-shaped inner surface(or any suitable shape presenting inclined wedging surfaces) formingupper and lower wedging surfaces 66 and 68. Pairs of upper and lowerinner shoes 70, 72 are formed with cam surfaces 74, 76 matingrespectively with said upper and lower annulus wedging surfaces 66, 68for sliding thereon. Compression spring means 78 is held captive inrecesses 80, 82 formed in the wedges 70, 72. Outside base control discs84, 86 are connected respectively to the annulus 64 and spring 78 byrods 88, 90 and must be pulled apart to enable release and ensuingadjustment of the shoes and wedges axially along the conductors 60 and62. It is contemplated further that, as shown in FIG. 4, finger strips92 and 94 may be added to the annular shoes 64 to improve electricalcontact and to maintain electrical contact when the outer conductor 62is out of round. The remainder of the elements are as in FIG. 3.

In FIG. 5 is shown another variant following the invention in which aninner segmented annulus holds captive in a V-shaped recess 102 a trainof outer upper and lower shoes 96 and 98. The spring biasing and rodarrangement remains the same.

This leads to the ultimate in preferred embodiment of the spring biasedwedge means portion of the invention (FIG. 6) wherein an annulus 104 isformed with reversed V-shaped recesses 106 and 108 on the inner andouter peripheries to hold captive a train of inner upper and inner lowershoes 110, 112 and outer upper and outer lower shoes 114, 116. Captivecompression springs 118 and 120 are held captive in recessed portionsindicated of the associated pairs of shoes and the two sets of shoes arereleased by rods 122 and 124 being moved downwardly by plate 128 and rod126 being moved upwardly by plate 130. It is to be noted that in thecase of the arrangement of FIG. 6 the annulus 104 (annular race) issolid, rather than being composed of a train of segments as indicated inFIG. 38, so that the annulus 104 can serve as the mechanical base forthe multiple actuator rods.

It will be understood that various changes in the details andarrangements of parts, which have been herein described and illustratedin order to explain the nature of the invention, may be made by thoseskilled in the art within the principle and scope of the invention asexpressed in the appended claims.

What is claimed is:

1. An improved cavity type ultra high frequency impedance adjustmentmeans comprising:

wave guide means having outer and inner concentric walls defining atuning cavity therebetween,

a coaxial feed transmission line having inner and outer conductors andhaving a relatively small cross-section in comparison to said wave guidemeans,

said coaxial feed line terminated within said wave guide means to formthereof an incoming section and a tuning section with said incomingsection outer conductor connected to said outer wave guide means walland said tuning section outer conductor connected to said inner waveguide means wall,

a shorting disc slidably connected between said inner and outerconductors of said tuning section of said feed line,

said shorting dis'c comprising radially moveable spring-biased wedgemeans for locking said shorting disc in fixed adjusted seated position,and

operating means connected to said spring to release said wedge bias whensaid disc is to be moved for impedance adjustment.

2. Apparatus according to claim 1 wherein said spring biased wedge meansincludes an annulus split to form inclined adjacent wedging surfaces andsegmented to form combinations of inner and outer annulus wedgesegments,

a tension spring for each combination of wedging segments,

said segments being recessed to hold said tension spring in captiveposition to bias said wedge segments in wedging position respectivelyagainst said outer and inner conductors of said feed line.

3. Apparatus according to claim 1 wherein said spring biasing wedgemeans includes an annulus segmented to form outer shoes, each shoe beingrecessed to form a V-shaped inner surface forming upper and lowerwedging surfaces,

pairs of upper and lower inner shoes having cam surfaces matingrespectively with said upper and lower annulus wedging surfaces forsliding thereon,

compression spring means,

said sliding wedges being recessed to hold said compression springcaptive between said sliding upper and lower inner shoes.

4. Apparatus according to claim 3 including spring-biased finger tipsprovided on said outer shoes to improve extent and reliability ofsatisfactory contact with said outer conductor.

5. Apparatus according to claim 1 wherein said spring-biased wedge meansincludes an annulus segmented to form inner shoes, each shoe beingrecessed to form a V-shaped outer surface forming upper and lowerwedging surfaces,

pairs of upper and lower outer shoes having cam surfaces matingrespectively with said upper and lower annulus wedging surfaces forsliding thereon,

compression spring means,

said sliding wedges being recessed to hold said compression springcaptive between said sliding upper and lower oute'r shoes.

6. Apparatus according to claim 1 wherein said spring biased wedge meansincludes an annulus having an outer and an inner peripheral V-shapedrecess,

pairs of upper and lower inner shoes having cam sur faces mating withsaid inner peripheral V-shaped recess and pairs of upper and lower outershoes having cam surfaces mating with said outer peripheral V-shapedrecess, forming double opposed wedge trains are for contacting saidinner conductor and are for contacting said outer conductor,

a compression spring means for each of said shoe pairs each pair ofshoes being recessed to hold its associated compression spring captive.

[SEAL] UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION patent3,'9.04 ,995' Dated September 9 1975 Edwin N. Phillips Inventor(s) It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

In the Abstract, line 3, after "providing" and before "the" insert ashorting disc slidably connected between Signed and Scaled this Attest:

RUTH C. MASON C. IAISIIALL DANN Arresting Office! Commission" of File.and Trademarks thirtieth Day of December 1975

1. An improved cavity type ultra high frequency impedance adjustmentmeans comprising: wave guide means having outer and inner concentricwalls defining a tuning cavity therebetween, a coaxial feed transmissionline having inner and outer conductors and having a relatively smallcross-section in comparison to said wave guide means, said coaxial feedline terminated within said wave guide means to form thereof an incomingsection and a tuning section with said incoming section outer conductorconnected to said outer wave guide means wall and said tuning sectionouter conductor connected to said inner wave guide means wall, ashorting disc slidably connected between said inner and outer conductorsof said tuning section of said feed line, said shorting disc comprisingradially moveable spring-biased wedge means for locking said shortingdisc in fixed adjusted seated position, and operating means connected tosaid spring to release said wedge bias when said disc is to be moved forimpedance adjustment.
 2. Apparatus according to claim 1 wherein saidspring biased wedge means includes an annulus split to form inclinedadjacent wedging surfaces and segmented to form combinations of innerand outer annulus wedge segments, a tension spring for each combinationof wedging segments, said segments being recessed to hold said tensionspring in captive position to bias said wedge segments in wedgingposition respectivelY against said outer and inner conductors of saidfeed line.
 3. Apparatus according to claim 1 wherein said spring biasingwedge means includes an annulus segmented to form outer shoes, each shoebeing recessed to form a V-shaped inner surface forming upper and lowerwedging surfaces, pairs of upper and lower inner shoes having camsurfaces mating respectively with said upper and lower annulus wedgingsurfaces for sliding thereon, compression spring means, said slidingwedges being recessed to hold said compression spring captive betweensaid sliding upper and lower inner shoes.
 4. Apparatus according toclaim 3 including spring-biased finger tips provided on said outer shoesto improve extent and reliability of satisfactory contact with saidouter conductor.
 5. Apparatus according to claim 1 wherein saidspring-biased wedge means includes an annulus segmented to form innershoes, each shoe being recessed to form a V-shaped outer surface formingupper and lower wedging surfaces, pairs of upper and lower outer shoeshaving cam surfaces mating respectively with said upper and lowerannulus wedging surfaces for sliding thereon, compression spring means,said sliding wedges being recessed to hold said compression springcaptive between said sliding upper and lower outer shoes.
 6. Apparatusaccording to claim 1 wherein said spring biased wedge means includes anannulus having an outer and an inner peripheral V-shaped recess, pairsof upper and lower inner shoes having cam surfaces mating with saidinner peripheral V-shaped recess and pairs of upper and lower outershoes having cam surfaces mating with said outer peripheral V-shapedrecess, forming double opposed wedge trains are for contacting saidinner conductor and are for contacting said outer conductor, acompression spring means for each of said shoe pairs each pair of shoesbeing recessed to hold its associated compression spring captive.